Last weekend I upgraded (using preupgrade) both my laptop and development box from 14 to 15. Both are x86_64 machines. On the laptop, twice now while rebooting the system has crashed with a stacktrace on the screen. Both times it occurred while the blue, light- blue and white progress bars were making their way across the screen. I do not know howto capture the stacktrace. The machine freezes. Ctl-Alt-Del does not cause a reboot. The offswitch does not work. After trying both of the above and waiting a couple of minutes, the machine turns off. Afterwards, I attempt another reboot and it works. Must be some timing issue. (The first time it happened was during the reboot at the end of the preupgrade process - needless to say my stress levels spiked.) Secondly, on my development machine I have a 4TB drive that I always mounted manually; its not in the /etc/fstabs file. Well, while rebooting at the end on the preupgrade process, I got the following popup: Dirty File Systems The following file systems for your Linux system were not unmounted cleanly. Please boot your Linux installation, let the file systems be checked and shut down cleanly to upgrade. /dev/sde1 Clicking OK, I was booted into 14. I then ran fsck on the disk which took many hours with no errors. Then, had to re-run the preupgrade script (which was much faster the second time since things had already been downloaded) and the reboot took me to 15. You might consider letting folks know on the preupgrade webpage that all disks, not just those in fstabs, HAVE to have had fsck run recently (don't know what recent means in this case). Lastly, the fonts are, well, not what they were before the upgrade. Others have mentioned this and I will live with them until some future time. Other than those issues, great upgrade process. Many Thanks! Richard